Method and system for fabricating a nano-structure

ABSTRACT

A method and system for fabricating nano-scale structures, such as channels (i.e., nano-channels) or vias (i.e., nano-vias). An open nano-structure, is formed in a substrate. Thereafter, a conformal material film may be deposited within and over the nano-structure using an optional first deposition process condition, and then the open nano-structure is closed off to form a closed nano-scale structure using a second deposition process condition, including one or more process steps.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 11/xxx,xxx, entitled “Method for Fabricating Nano-Structures”,Attorney docket no. 313530-P0033US, filed on even date herewith. Theentire contents of this application are herein incorporated by referencein their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a closed structure and a method forfabricating the closed structure, and more particularly to a closedfluidic structure, such as a closed fluidic channel, and a method offabricating a closed fluidic structure in a substrate using vapordeposition techniques.

2. Description of Related Art

Nano-structures, such as nano-fluidic devices andnano-electro-mechanical systems (NEMs) (i.e., fluidic devices orelectro-mechanical devices having cross-sectional dimensions fabricatedat the nanometer scale), are an emerging technological field havingsignificant commercial potential for the future. Nano-structures,including nano-fluidic devices having arrays of nano-scale channels, arecontemplated for use in molecular/biological sensors, biologicalseparations and catalysis, single cell analysis, single moleculemanipulation, DNA stretching, nano-scale fluidic transport, and highthroughput macro-molecular analysis.

As an example, an array of nano-scale channels may facilitate themanipulation and analysis of bio-molecules, including DNA (having apersistence length of approximately 50 nm), proteins, etc. These arraysof nano-scale channels may possess channels of varying sizes, whereineach size, e.g., the cross-sectional dimensions of the channel, isselected for the passage of a specific molecular cross-section.Therefore, a pre-determined arrangement of the array of channels ofvarying size can permit the filtering of bio-molecules of differentsize.

In yet another example, nano-fluidic devices are contemplated forconductive-convective cooling of micro- and/or nano-electronic devices.Due to the continuing reduction in electronic structure size and theincreasing number density of devices on substrate real estate, thedensity of dissipated power increases, while the need to remove thisheat becomes increasingly important in order to preserve the operatingcharacteristics of the electronic device.

SUMMARY OF THE INVENTION

The present invention relates to a nano-structure, and a method andsystem for fabricating a closed nano-structure.

According to one embodiment, an open nano-structure is formed on asubstrate and the nano-structure is closed using a vapor depositiontechnique.

According to another embodiment, the open nano-structure formed in thesubstrate comprises a trench or via having a characteristic dimensionless than or equal to approximately 500 nanometers (nm). In yet anotherembodiment, the characteristic dimension is less than or equal toapproximately 200 nm.

According to another embodiment, a nano-fluidic structure is formed on asubstrate having precise cross-sectional dimensions and a method isdescribed for forming the nano-fluidic structure.

Still another embodiment of the invention is to provide a method offorming an interconnection of two or more nano-fluidic structures on asubstrate.

These and/or other embodiments of the invention may be provided by amethod of fabricating a closed structure on a substrate, in which anopen feature is formed within the substrate. The open feature extendsinto the substrate from an opening at an upper surface thereof and has anominal cross-sectional shape characterized by an initial lateraldimension that is less than or equal to approximately 500 nanometers(nm). The opening to the open feature is closed in order to create aclosed feature in the substrate by using one or more vapor depositionprocesses to deposit material across the opening thereby forming amaterial membrane closing the opening to the open structure. Thematerial deposited across the opening and within the open feature issuch that a resultant cross-sectional shape of the closed feature issubstantially the same as the nominal cross-sectional shape.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1A illustrates a method of forming a nano-scale structure accordingto one embodiment;

FIG. 1B illustrates a method of forming a nano-scale structure accordingto another embodiment;

FIGS. 2A through 2G depict a method of forming a nano-scale structure ona substrate according to yet another embodiment;

FIG. 3 illustrates a flow chart of a method for forming a nano-scalestructure on a substrate according to an embodiment;

FIG. 4 illustrates a flow chart of a method for forming a nano-scalestructure on a substrate according to another embodiment;

FIGS. 5A through 5E depict a method for forming a nano-scale structurein a substrate according to yet another embodiment;

FIG. 6 provides an illustrative diagram for performing a vapordeposition process to close an open nano-scale structure;

FIG. 7 presents an exemplary SEM photograph of a closed nano-scalestructure; and

FIG. 8 presents a deposition system for forming a nano-scale structureaccording to an embodiment.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

In the following description, in order to facilitate a thoroughunderstanding of the invention and for purposes of explanation and notlimitation, specific details are set forth, such as a particulargeometry of a nano-scale structure having an open or closed feature anddescriptions of various processes for forming the open or closedstructure. However, it should be understood that the invention may bepracticed in other embodiments that depart from these specific details.

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, FIGS. 1Aand 1B, and FIG. 3 illustrate a method for forming a nano-scalestructure according to several embodiments. As shown in FIG. 3, themethod is illustrated in a flow chart 200, wherein the method comprisesforming an open feature in a substrate in at 210, and using vapordeposition techniques to close the open feature in at 220 whilepreserving the cross-sectional shape, or the internal criticaldimension(s) (CD), or both the shape and CDs of the (e.g., nano-scale)feature cross-section.

According to one embodiment, the use of vapor deposition techniques toclose the open feature can include the formation of a homogeneous (e.g.,nano-scale) closed feature, whereby the deposited material forms acontinuous (vapor deposited) material boundary enclosing the featurevoid (e.g., channel void or via void); see FIG. 1A. According to anotherembodiment, the use of vapor deposition techniques to close the openfeature can include the formation of a heterogeneous (e.g., nano-scale)closed feature, whereby the deposited material forms only a membrane (orcapping) layer to close the open end of the open feature without forminga continuous (vapor deposited) material boundary (i.e., non-continuousmaterial boundary) enclosing the feature void (e.g., channel void or viavoid); see FIG. 1B.

For the heterogeneous closed feature, when forming a thin materialmembrane across an open feature, material can be deposited within theopen feature on the feature sidewalls, or the bottom, or both. In eitherthe case of homogeneous closed features or heterogeneous closedfeatures, such deposition can be controlled in order to prepare closedfeatures having desired internal dimensions so that the practical use ofsuch features as, for example, nano-fluidic arrays in heat transfersystems for electronic devices, bio-molecule filtering systems, etc.,can be realized. As will be described, vapor deposition processes aredescribed that can preserve one or more of the internal dimensions orshape or both when closing the open feature (i.e., forming the thinmaterial membrane).

As illustrated in FIGS. 1A and 1B, an open feature 12 (12′) is formed ina substrate 10. The open feature 12 (12′) extends into the substrate 10from an opening at an upper surface thereof and comprises a nominalcross-sectional shape characterized by an initial lateral dimension. Forexample, the open feature 12 (12′) can include an open channel ortrench, or alternatively, the open feature 12 (12′) can include a via orhole.

The open feature 12 (12′) may comprise a substantially rectangularcross-sectional shape, such as the square cross-section illustrated inFIGS. 1A and 1B, or it may comprise a more circular, rectangular ortrapezoidal cross-section, for example. The cross-sectional shape may beof any shape that can be achieved using conventional techniques known tothose skilled in the art of micro/nano-scale etching, imprinting,milling, etc. The initial lateral dimension can include a width, ormaximum lateral extent of the open feature 12 (12′) in substrate 10.Alternatively, the initial lateral dimension can include a diameter.Additionally, the nominal cross-sectional shape can be characterized byan initial vertical dimension. The initial vertical dimension mayinclude a depth, or maximum vertical extent of the open feature 12 (12′)into substrate 10.

The open feature 12 (12′) may be formed using any technique, such as anetching process, a milling process, or a (nano-)imprint lithographyprocess, or a combination thereof. The etching process can include a dryetching process with or without plasma, or a wet etching process. Forexample, when an anisotropic feature (i.e., a substantially rectangularcross-sectional shape) is desired, a dry plasma etching process, such asa reactive ion etching process, may be used. Alternatively, for example,when an isotropic feature is desired, a wet etching process may be used.

As illustrated in FIG. 1A for a homogeneous closed feature, the initiallateral dimension of the open feature can be characterized by width (a),and the initial vertical dimension of the open feature can becharacterized by depth (c). In order to facilitate the use of vapordeposition techniques to form a (homogeneous or heterogeneous, i.e.,FIG. 1A or 1B) closed feature, the initial lateral dimension (a) of theopen feature 12 (12′) is selected to be less than or equal toapproximately 500 nanometers (nm), and desirably, it is selected to beless than or equal to approximately 200 nm. However, features of lateraldimensions greater than approximately 500 nm can be closed using vapordeposition techniques and will be discussed later.

Additionally, for instance, the initial vertical dimension of the openfeature 12 (12′) may be of any dimension suitable for the specificapplication. The initial vertical dimension may be very small, on theorder of several nanometers (nm), or it may be larger on the order ofseveral microns and greater.

Once the open feature 12 (12′) is formed in substrate 10, it may beclosed using one or more vapor deposition processes. In one embodiment,as shown in FIG. 1A, a continuous layer 20 of material is formed, thuscreating feature void 15. Alternatively, in another embodiment, anon-continuous layer 20′ is formed, thus creating feature void 15′. Anyvapor deposition process may be employed including one or more ofphysical vapor deposition (PVD), ionized PVD (iPVD), ionized vapordeposition, chemical vapor deposition (CVD), plasma enhanced CVD(PECVD), atomic layer deposition (ALD), or plasma enhanced ALD (PEALD),or a combination of two or more thereof. Furthermore, the vapordeposition processes may comprise multiple steps configured to adjustthe net amount of deposition on various surfaces of the substrate bybalancing deposition and etching mechanisms. Moreover, the amount of netdeposition on the flat-field or any of the feature surfaces, such as thesidewalls or bottom, can be adjusted by tailoring the vapor depositionprocesses accordingly (to be discussed below).

Ionized deposition processes or ionized PVD processes can be utilized toclose the open feature, thus forming the closed feature. In these vapordeposition techniques for forming the material membrane closing the openfeature, the adatom (i.e., material to be deposited), or a fraction ofthe adatom, is ionized. The adatom may be introduced by sputtering, orit may be introduced in vapor form using other techniques, includingelectron beam heating, laser heating, radio frequency (RF) inductionheating, resistive heating, etc.

The material that is selected for forming the homogeneous orheterogeneous closed feature may be (electrically) conductive,semi-conductive or non-conductive. Additionally, a material may beselected for its reactive or non-reactive properties. For example, thematerial may comprise a metal (M), metal oxide (M_(x)O_(y)), metalnitride (M_(x)N_(y)), metal silicide (M_(x)Si_(y)), metal silicate(M_(x)Si_(y)O_(z)), metal oxynitride (M_(x)O_(y)N_(z)), etc.Additionally, for example, a metal may be selected for its reactive orcatalytic properties.

For example, as illustrated in FIG. 1A, once the feature is closed, theinternal lateral dimension of the closed feature can be characterized bywidth (b), and the internal vertical dimension of the closed feature canbe characterized by depth (d). Additionally, for example, the thicknessof the vapor deposited membrane to close the feature can becharacterized by thickness (e).

The vapor deposition processes may be performed such that thecross-sectional shape of the feature void is geometrically similar tothe nominal shape of the open feature 12. For instance, the finallateral dimension (b) can be greater than or equal to approximately 50%of the initial lateral dimension (a), or the final lateral dimension (b)can be greater than or equal to approximately 80% of the initial lateraldimension (a). Alternatively, the final lateral dimension (b) can begreater than or equal to approximately 90% of the initial lateraldimension (a). Additionally, for instance, the final vertical dimension(d) can be greater than or equal to approximately 50% of the initialvertical dimension (c), or the final vertical dimension (d) can begreater than or equal to approximately 80% of the initial verticaldimension (c). Alternatively, the final vertical dimension (d) can begreater than or equal to approximately 90% of the initial verticaldimension (c). Furthermore, for instance, the thickness (e) of membraneclosing the open feature can range from approximately 1 nm toapproximately 1000 nm, or the thickness can range from approximately 5nm to approximately 50 nm.

Referring now to FIGS. 2A through 2G and FIG. 4, a method is describedfor closing an open feature on a substrate according to anotherembodiment. As shown in FIG. 4, the method is illustrated in a flowchart 300, wherein the method comprises forming an open feature 110 in asubstrate 100 at 305. The open feature 110 may be formed using any ofthe techniques described above.

At 310 and as shown in FIG. 2B, an optional conformal material layer 120is deposited on the open feature 110. Once the feature 110 (withconformal material layer 120) is closed, a homogeneous closed feature isformed as in FIG. 1A. Alternatively, once the feature 110 (withoutconformal material layer 120) is closed, a heterogeneous closed featuremay be formed as in FIG. 1B. The conformal material layer 120 may beformed using any of the vapor deposition techniques described above. Forexample, an ALD process, a CVD process, or an ionized vapor depositionprocess, such as an ionized PVD process, may be utilized to form theconformal material layer 120. Additionally, for example, when using aniPVD process, a process condition creating a high ratio of adatom ionpopulation to total adatom population (i.e., approaching unity) with lowion energy (e.g., low substrate bias), such that etching of depositedadatom is decreased or substantially absent, may be utilized to producea conformal thin film. An exemplary set of process conditions will bedescribed in greater detail later for an iPVD process.

At 320 and as shown in FIG. 2C, an overhang material layer 130 isdeposited to form an overhang 132 at the opening to the open feature110. At 330 and as shown in FIG. 2D, a membrane layer 140 is depositedto form a bridge 142 across the opening to the open feature 110, thusclosing off an internal void 144. For example, an ionized vapordeposition process, such as an ionized PVD process, may be utilized toform the overhang material layer 130 or the membrane layer 140 or both.Additionally, when using an iPVD process, a process condition creating arelatively lower ratio of adatom ion population to total adatompopulation (e.g., increased total adatom population with substantiallythe same adatom ion population) with a relatively higher ion energy(e.g., high substrate bias), such that etching of deposited adatom isincreased or substantially near a no net deposition condition in theflat-field, may be utilized to produce the overhang layer 130 or themembrane layer 140 or both. An exemplary set of process conditions willbe described in greater detail later for an iPVD process.

The processes illustrated at 320 and 330 in FIG. 4 may be performed atthe same time using the same process conditions (i.e., process recipe),or they may be performed separately using more than one set of processconditions. For example, when the process conditions are different forthe formation of the overhang layer 130 and the formation of themembrane layer 140, the total adatom population created for forming theoverhang layer 130 may be decreased during the creation of the membranelayer 140.

At 340 and as shown in FIG. 2E, an optional thickening material layer150 is deposited. For example, an ALD process, a CVD process, or anionized vapor deposition process, such as an ionized PVD process, may beutilized to form the thickening material layer 150. An exemplary set ofprocess conditions will be described in greater detail later for an iPVDprocess.

At 350 and as shown in FIG. 2F, the material deposited on substrate 100may be planarized to form a planar surface 160. The planarizationprocess may include a chemical-mechanical polishing (CMP) process.

Furthermore, as illustrated in FIG. 2G, an opening 170 may, optionally,be formed in the closed feature. The opening may, for example, be formedusing an etching or milling process. Additionally, the opening may, forexample, include a variety of cross-sectional shapes, includingcircular, elliptical, rectangular, square, or any shape that can bepatterned using, for instance, a photo-lithography process.

According to yet another embodiment, FIGS. 5A through 5D illustrate amethod for forming a closed feature having an internal lateral dimensiongreater than approximately 500 nm. As shown in FIG. 5A, a substrate 400includes a cap layer 410 and a mask layer 420 having pattern 425 formedthereon. Cap layer 410 comprises a material composition sufficientlydifferent than said substrate 400 such that one material may beselectively etched relative to the other material. As described above,the lateral critical dimension (i.e., width (a) of the opening in masklayer 420, as shown in FIG. 5C) of pattern 425 is selected to beapproximately 500 nm or less.

As shown in FIG. 5B, the pattern 425 is transferred to the cap layer 410and the substrate 400 using one or more etching processes, such as oneor more anisotropic dry plasma etching processes. Thereafter, asillustrated in FIG. 5C, a selective etching process is performed inorder to laterally etch substrate 400 in order to increase the nominallateral critical dimension (a) of pattern 425 to an expanded lateralcritical dimension (a′).

Once the expanded open feature is formed in substrate 400 having a width(a′) and an opening (a), any remaining mask layer 420 can be removed andone or more vapor deposition processes can be executed to form membranelayer 430 to close the open feature as illustrated in FIG. 5D. When thematerial composition of membrane layer 430 is different than thematerial composition of cap layer 410, the closure mechanism may besimilar to that illustrated in FIG. 5D, i.e., material deposited in theflat-field.

Alternatively, as illustrated in FIG. 5E, the open feature may be closedby depositing a bridge layer 432. When the material composition ofmembrane layer 430 is the same as the material composition of cap layer410, the closure mechanism may be similar to that illustrated in FIG.5E, i.e., less material deposited in the flat-field.

Referring now to FIG. 8, a deposition system 500 is presented accordingto an embodiment of the invention. Deposition system 500 includes aprocess chamber 510, and a substrate holder 512 coupled to the processchamber 510, and configured to support a substrate 514. Additionally,the deposition system 500 includes a plasma source 520 coupled to theprocess chamber 510 and configured to form plasma in process space 540within process chamber 510. Additionally, the deposition system 500includes an adatom source 530 coupled to the process chamber 510, andconfigured to introduce an adatom to process space 540 in processchamber 510.

The deposition system 500 can further comprise a gas injection system560 coupled to the process chamber 510, and configured to introduce aninert gas, such as a noble gas (i.e., helium, argon, xenon, krypton,etc.), to the process space 540 in process chamber 510. Optionally, thedeposition system 500 can further comprise a control system 550 coupledto the process chamber 510, the substrate holder 512, the plasma source520, and the adatom source 530, wherein it may be configured to performat least one of operating, adjusting, monitoring, or controlling thedeposition system 500 according to, for example, a process recipe.

Referring still to FIG. 8, plasma source 520 can include an electrodecoupled to a power source, such as a radio frequency (RF) generator, ora coil antenna coupled to a power source, such as a helical coil orother antenna coupled to an RF generator. For example, the plasma source520 can include a capacitively coupled plasma (CCP) source, or aninductively coupled plasma source (ICP), or combination thereof.Additionally, for example, sub- and atmospheric ICP sources generateplasma with electron density of approximately n_(e)≈(1−4)×10¹⁴ cm⁻³ andelectron temperature of approximately ˜0.2 eV to approximately 0.6 eVwith 100% ionization of the adatom. Alternately, plasma source 120 caninclude a source capable of production of large area plasmas, such aselectron beam sources with low electron temperature and electron densityof approximately n_(e)≈1.2×10¹² cm⁻³ and above, as well as those capableof high density flat plasma production based on surface waves, helicon,or electron cyclotron resonance (ECR) plasma sources.

Adatom source 530 can, for example, be distributed about the perimeterof process chamber 510, from which source material adatoms enter processspace 540. The source material can include conductive material,semi-conductive material, or non-conductive material. For example, ametal target may be utilized as a source of metal. The target can bebiased using direct current (DC), or alternating current (AC) togenerate adatoms (of source material) through a sputtering process.Alternately, other adatom sources, such as magnetrons, can be used.Pulsed laser deposition, high power pulsed magnetron sputtering, plasmaassisted sputter techniques, etc., can be utilized. Additionally, theadatom source 530 can include a plurality of adatom sources. Theplurality of adatom sources can be coupled to a power source.Alternately, each adatom source can be independently coupled to aseparate power source. Alternately, the power can be alternatingly andsequentially coupled to the plurality of metal sources using one or morepower sources.

Substrate holder 512 can include an electrode through which AC power,such as RF power, or DC power, or both is coupled to substrate 514. Forexample, substrate holder 512 can be electrically biased at an RFvoltage via the transmission of RF power from an RF generator through animpedance match network to substrate holder 512. The RF bias can serveto heat electrons to form and maintain plasma. Alternatively, the RFbias can serve to affect the ion energy of ions incident on the uppersurface of the substrate. A typical frequency for the RF bias can rangefrom 0.1 MHz to 100 MHz. RF systems for plasma processing are well knownto those skilled in the art. Alternately, RF power is applied to thesubstrate holder electrode at multiple frequencies. Furthermore, animpedance match network can serve to improve the transfer of RF power toplasma in the process chamber by reducing the reflected power. Matchnetwork topologies (e.g. L-type, π-type, T-type, etc.) and automaticcontrol methods are well known to those skilled in the art.

Additionally, the substrate holder 512 can comprise an electrostaticclamping system (or mechanical clamping system) in order to electrically(or mechanically) clamp substrate 514 to the substrate holder 512.Furthermore, substrate holder 512 can, for example, further include acooling system having a re-circulating coolant flow that receives heatfrom substrate holder 512 and transfers heat to a heat exchanger system(not shown), or when heating, transfers heat from the heat exchangersystem. Moreover, a heat transfer gas can, for example, be delivered tothe back-side of substrate 514 via a backside gas system to improve thegas-gap thermal conductance between substrate 514 and substrate holder512. For instance, the heat transfer gas supplied to the back-side ofsubstrate 512 can comprise an inert gas such as helium, argon, xenon,krypton, a process gas, or other gas such as oxygen, nitrogen, orhydrogen. Such a system can be utilized when temperature control of thesubstrate is required at elevated or reduced temperatures. For example,the backside gas system can comprise a multi-zone gas distributionsystem such as a two-zone (center-edge) system, wherein the back-sidegas gap pressure can be independently varied between the center and theedge of substrate 514. In other embodiments, heating/cooling elements,such as resistive heating elements, or thermoelectric heaters/coolerscan be included in the substrate holder 512, as well as the chamber wallof the process chamber 510.

Furthermore, control system 550 can include a microprocessor, memory,and a digital I/O port capable of generating control voltages sufficientto communicate and activate inputs to deposition system 500 as well asmonitor outputs from deposition system 500. Moreover, control system 550can be coupled to and can exchange information with process chamber 510,plasma source 520, distributed metal source 530, gas injection system560, and vacuum pump system (not shown). For example, a program storedin the memory can be utilized to activate the inputs to theaforementioned components of deposition system 500 according to aprocess recipe in order to perform a deposition process. One example ofcontrol system 550 includes a DELL PRECISION WORKSTATION 610™, availablefrom Dell Corporation, Austin, Tex.

However, the control system 550 may be implemented as a general purposecomputer system that performs a portion or all of the microprocessorbased processing steps of the invention in response to a processorexecuting one or more sequences of one or more instructions contained ina memory. Such instructions may be read into the controller memory fromanother computer readable medium, such as a hard disk or a removablemedia drive. One or more processors in a multi-processing arrangementmay also be employed as the controller microprocessor to execute thesequences of instructions contained in main memory. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.

The control system 550 may be locally located relative to the depositionsystem 500, or it may be remotely located relative to the depositionsystem 500. For example, the control system 550 may exchange data withthe deposition system 500 using at least one of a direct connection, anintranet, the Internet and a wireless connection. The control system 550may be coupled to an intranet at, for example, a customer site (i.e., adevice maker, etc.), or it may be coupled to an intranet at, forexample, a vendor site (i.e., an equipment manufacturer). Additionally,for example, the control system 550 may be coupled to the Internet.Furthermore, another computer (i.e., controller, server, etc.) mayaccess, for example, the control system 550 to exchange data via adirect connection, an intranet, or the Internet or any combinationthereof. As also would be appreciated by those skilled in the art, thecontrol system 550 may exchange data with the deposition system 500 viaa wireless connection.

According to one example, the deposition system 500 comprises an ionizedphysical vapor deposition (iPVD) system. Further details of an iPVDsystem are described in U.S. Pat. No. 6,719,886 B2, entitled “Method andapparatus for ionized physical vapor deposition”, the entire contentsare incorporated herein by reference in their entirety.

In the following discussion, a method of closing an open featureutilizing an ionized vapor deposition system is presented. For example,the ionized vapor deposition system may include an iPVD systemconfigured to deposit metal-containing films, such as the iPVD systemhaving various elements that is described in FIG. 8.

In an embodiment, the method of closing the open feature to form aclosed feature comprises using a metal-containing target electrode. Thetarget electrode comprises the material to be deposited (i.e., adatom)on the substrate. For example, when depositing copper (Cu) or tantalum(Ta), the target comprises Cu or Ta, respectively. An iPVD processparameter space can comprise: a chamber pressure of approximately 5mTorr to approximately 1000 mTorr (desirably, the chamber pressureranges from approximately 50 mTorr to approximately 100 mTorr); a noblegas (e.g., argon) flow rate (i.e., from gas injection system 560)ranging from approximately 50 to approximately 5000 sccm (alternatively,the flow rate ranges from approximately 200 sccm to approximately 600sccm); a (direct current, DC) target power (i.e., adatom source 530power in FIG. 8) ranging from approximately 5 kW to approximately 20 kW(alternatively, the DC power ranges from approximately 10 kW toapproximately 15 kW); a plasma source radio frequency (RF) power (i.e.,plasma source 520 power in FIG. 8) ranging from approximately 0.5 kW toapproximately 10 kW (alternatively, the plasma source RF power rangesfrom approximately 4 kW to approximately 6 kW); a substrate holder RFbias (i.e., substrate holder 512 RF power) ranging up to approximately 2kW (alternatively, the substrate holder RF bias power can range fromapproximately 100 W to approximately 1000 W); and a deposition time (forforming the closed feature) ranging from approximately 30 second toapproximately 600 seconds (alternatively, the deposition time rangesfrom approximately 60 seconds to approximately 180 seconds).

Referring now to FIG. 6, an illustrative diagram is presented to providean example of the method for closing an open feature as described inFIG. 4 using the system described in FIG. 8. The diagram presents anexemplary relationship between the amount of deposition on the substrate(e.g., in the flat-field) versus the substrate bias power (e.g.,substrate holder RF power) on the abscissa and the target power (e.g.,DC target power). For instance, as the substrate bias power is increasedwhile holding other process parameters constant (e.g., pressure, plasmasource power, etc.), the deposition amount remains substantially flatuntil it begins to decay once the ion energy for ions incident on thesubstrate is sufficiently high to sputter (or physically etch) adatomfrom the substrate. Eventually, at a very high substrate bias power, ano net deposition condition is reached (i.e., substantially zero netdeposition in the flat-field). Additionally, as the target powerdecreases while holding other process parameters constant, the processcondition shifts from the upper curve (solid line) to the lower curve(dashed line). By decreasing the target power and maintaining the samepressure and plasma source power (i.e., Ar ion population), the totaladatom population is decreased, but with the same Ar ion ionizationcondition, the adatom ion population is increased and, hence, the ratioof the adatom ion population relative to the total adatom population isincreased.

When performing the optional step 310 using an iPVD process, a processcondition creating a high ratio of adatom ion population to total adatompopulation (i.e., approaching unity) with low ion energy (e.g., lowsubstrate bias), such that etching of deposited adatom is decreased orsubstantially absent, may be utilized to produce a conformal thin film.For instance, in order to achieve a high ratio of adatom ion populationto total adatom population, the (DC) target power can be reduced (e.g.,less than or equal to approximately 10 kW) to reduce the amount ofadatom produced by sputtering and the plasma source RF power (e.g., RFICP power) can be increased to increase ionization, while the substratebias power is decreased (e.g., less than or equal to approximately 500W) to avoid operating in an etching regime, as illustrated by condition310′ in FIG. 6. The higher adatom ion population (relative tonon-ionized adatom population) is beneficial for conformal depositionover substrate topography.

When performing the overhang step 320 or bridge step 330 or both usingan iPVD process, a process condition creating a relatively lower ratioof adatom ion population to total adatom population (e.g., increasedtotal adatom population with substantially the same adatom ionpopulation) with a relatively higher ion energy (e.g., high substratebias), such that etching of deposited adatom is increased orsubstantially near a no net deposition condition in the flat-field, maybe utilized to produce the overhang layer 130 or the membrane layer 140or both. For instance, the (DC) target power can be increased (e.g.,greater than or equal to approximately 10 kW) to increase the amount ofadatom produced by sputtering, the plasma source power (e.g., RF ICPpower) can be increased (e.g., greater than or equal to approximately5000 W) to increase ionization, while the substrate bias power isincreased (e.g., greater than approximately 500 W) to operate in anetching regime, as illustrated by condition 320′ and 330′ in FIG. 6. Asillustrated in FIG. 6, process conditions 320′ and 330′ may bedifferent, and may, for example, lie within the cross-hatched region.Process condition 330′ may be performed after process condition 320′ ata higher bias power, where the bias powers of both process conditionsare greater than approximately 500 W.

When performing the optional step 340 using an iPVD process, a processcondition creating a high adatom ion population and high adatompopulation with low ion energy (e.g., low substrate bias), such thatetching of deposited adatom is decreased or substantially absent, may beutilized to produce a thickening thin film. For instance, in order toachieve a high adatom ion population and a high total adatom population,the (DC) target power can be increased to increase the amount of adatomproduced by sputtering and the plasma source RF power (e.g., RF ICPpower) can be increased to increase ionization, while the substrate biaspower is decreased (e.g., less than or equal to approximately 500 W) toavoid operating in an etching regime, as illustrated by condition 340′in FIG. 6.

As an example, a method of closing an open feature to form a closedfeature utilizing an iPVD system such as the one described in FIG. 8 andin U.S. Pat. No. 6,719,886 B2 is presented. However, the methodsdiscussed are not to be limited in scope by this exemplary presentation.FIG. 7 presents a SEM (scanning electron microscope) photograph of aclosed trench formed by a copper (Cu) iPVD system utilizing thefollowing exemplary process condition to simultaneously perform onlysteps 330 and 340 in FIG. 4: Chamber pressure=65 mTorr; Argon flow rate˜500 sccm; Target DC power ˜10-12 kW; ICP (inductively coupled plasma)coil RF power=5-6 kW; Substrate RF bias power ˜800-900 W; and Backsideargon pressure=5 Torr; and a deposition time of approximately 120seconds. As shown in FIG. 7, a homogeneous closed feature is producedhaving enclosure walls that are substantially uniform in thickness.

Although only certain exemplary embodiments of inventions have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention.

1. A method of fabricating a closed structure on a substrate,comprising: forming an open feature within said substrate, said openfeature extending into said substrate from an opening at an uppersurface thereof and having a nominal cross-sectional shape characterizedby an initial lateral dimension that is less than or equal toapproximately 500 nanometers (nm); and closing said opening to said openfeature in order to create a closed feature in said substrate by usingone or more vapor deposition processes to deposit material across saidopening thereby forming a material membrane closing said opening to saidopen structure, wherein said material deposited across said opening andwithin said open feature is such that a resultant cross-sectional shapeof said closed feature is substantially the same as said nominalcross-sectional shape.
 2. The method of claim 1, further comprising:prior to said closing of said opening, depositing a conformal thin filmas a liner for said open feature.
 3. The method of claim 2, wherein thethickness of said material membrane is substantially the same as thethickness of said conformal thin film.
 4. The method of claim 1, whereinsaid closing of said opening further comprises producing a closedfeature having a final lateral dimension that is greater than or equalto approximately 80% of said initial lateral dimension.
 5. The method ofclaim 1, wherein said closing of said opening further comprisesproducing a closed feature having a final lateral dimension that isgreater than or equal to approximately 90% of said initial lateraldimension.
 6. The method of claim 1, wherein said closing of saidopening comprises closing said opening using one or more ionized vapordeposition processes.
 7. The method of claim 6, wherein said closing ofsaid opening comprises closing said opening using one or more ionizedphysical vapor deposition (iPVD) processes.
 8. The method of claim 1,wherein said forming of said open feature comprises forming an openfeature that is characterized by an initial lateral dimension less thanor equal to approximately 200 nanometers (nm).
 9. The method of claim 1,wherein said forming of said open feature comprises using an etchingprocess, a nano-imprint lithography process, or an ion milling process,or a combination of two or more thereof.
 10. The method of claim 9,wherein said etching process comprises using a wet etching process, adry etching process, a dry plasma etching process, or a laser-assistedetching process, or a combination of two or more thereof.
 11. The methodof claim 1, wherein said forming of said open feature comprises formingan open channel having two sidewalls opposing one another and extendingfrom said opening to a bottom of said open channel, and wherein saidnominal cross-sectional shape includes a substantially rectangularcross-section and said initial lateral dimension is characterized by thedistance between said opposing sidewalls of said open channel.
 12. Themethod of claim 11, wherein said closing of said opening comprisesforming said material membrane using an iPVD process.
 13. The method ofclaim 1, wherein said forming of said open feature comprises forming aplurality of open channels, each open channel having two sidewallsopposing one another and extending from said opening to a bottom of saidopen channel, and wherein said nominal cross-sectional shape includes asubstantially rectangular cross-section and said initial lateraldimension is characterized by the distance between said opposingsidewalls of said open channel.
 14. The method of claim 1, wherein saidforming of said open feature comprises forming an open channelcharacterized by a maximum lateral extent and a maximum vertical extent,and wherein said nominal cross-sectional shape includes a substantiallynon-rectangular cross-section and said initial lateral dimension ischaracterized by said maximum lateral extent of said open channel. 15.The method of claim 14, wherein said closing of said opening comprisesforming said material membrane using an iPVD process.
 16. The method ofclaim 1, wherein said forming of said open feature comprises forming anopen via having a cylindrically shaped sidewall extending from saidopening to a bottom of said open via, and wherein said nominalcross-sectional shape at a center of said open via includes asubstantially rectangular cross-section and said initial lateraldimension is characterized by the diameter of said open via.
 17. Themethod of claim 16, wherein said closing of said opening comprisesforming said material membrane using an iPVD process.
 18. The method ofclaim 1, wherein said closing of said open feature comprises: performingan optional first vapor deposition process to form a conformal materialfilm on said substrate and within said open feature; and following saidoptional first vapor deposition process, performing a second vapordeposition process to form said material membrane across said opening toclose said open feature.
 19. The method of claim 18, wherein saidperforming of said first vapor deposition process comprises performingan iPVD process or an atomic layer deposition (ALD) process or both. 20.The method of claim 18, wherein said performing of said second vapordeposition process comprises performing an ionized vapor depositionprocess or an iPVD process.
 21. The method of claim 1, furthercomprising: forming a through-hole in said closed feature.
 22. Themethod of claim 21, wherein said through-hole comprises a circularorifice or a rectangular orifice.
 23. The method of claim 1, whereinsaid closing of said open feature comprises: disposing said substrate ona substrate holder in an iPVD system, wherein said iPVD system isconfigured to: (a) provide bias power to said substrate holder, (b)provide source power to a plasma generation system configured to formplasma in said iPVD system, and (c) provide target power to a sputtertarget configured to introduce said material for said one or more vapordeposition processes; and performing a first iPVD process using a biaspower setting for said bias power greater than approximately 500 W. 24.The method of claim 23, wherein said first iPVD process further includesusing a target DC power setting greater than or equal to approximately10 kW.
 25. The method of claim 24, wherein said first iPVD processfurther comprises using a plasma source power setting, comprising a RFpower greater than or equal to approximately 5000 W.
 26. The method ofclaim 23, wherein said first iPVD process comprises performing a firstprocess step at a first bias power greater than approximately 500 W anda second process step at a second bias power greater than approximately500 W, and wherein said second bias power is greater than said firstbias power.
 27. The method of claim 23, further comprising: prior tosaid first iPVD process, performing a second iPVD process using a lowbias power setting for said bias power, wherein said low bias powersetting comprises a power less than or equal to approximately 500 W. 28.The method of claim 27, wherein said second iPVD process furtherincludes using a low target power setting, wherein said low target powersetting comprises a DC power less than or equal to approximately 10 kW.29. The method of claim 23, wherein said first iPVD process comprisesone or more metal vapor deposition processes.
 30. The method of claim23, further comprising: following said first iPVD process, performing athird iPVD process using another low bias power setting for said biaspower, wherein said low bias power setting comprises a power level lessthan or equal to approximately 500 W.
 31. The method of claim 23,further comprising: planarizing said material on said substrate to thesubstrate surface.
 32. A method of fabricating a closed nano-fluidicchannel on a substrate, comprising: forming an open channel within saidsubstrate, said open channel extending into said substrate from anopening at an upper surface thereof and having a nominal cross-sectionalshape characterized by an initial lateral dimension that is less than orequal to approximately 200 nanometers (nm); applying a conformal thinfilm of material to said open channel in order to form a contiguous filmon the surfaces of said open channel; and closing said opening to saidopen channel in order to create a closed nano-fluidic channel in saidsubstrate by using one or more iPVD processes to deposit material acrosssaid opening thereby forming a material membrane closing said opening tosaid open channel, wherein said material deposited across said openingand within said open channel is such that a resultant cross-sectionalshape is substantially the same as said nominal cross-sectional shape.33. A method of fabricating a closed nano-via on a substrate,comprising: forming a substantially cylindrical open via within saidsubstrate, said open via extending into said substrate from asubstantially circular opening at an upper surface thereof and having anominal cross-sectional shape characterized by an initial diameter thatis less than or equal to approximately 200 nanometers (nm); applying aconformal thin film of material to said open via in order to form acontiguous film on the surfaces of said open via; and closing saidopening to said open via in order to create a closed via in saidsubstrate by using one or more iPVD processes to deposit material acrosssaid opening thereby forming a material membrane closing said opening tosaid open via, wherein said material deposited across said opening andwithin said open via is such that a resultant cross-sectional shape issubstantially the same as said nominal cross-sectional shape.
 34. Anano-scale channel formed on a substrate, comprising: an open channelformed in said substrate, wherein said open channel extends into saidsubstrate from an opening at an upper surface thereof and comprises anominal cross-sectional shape characterized by an initial lateraldimension that is less than or equal to approximately 200 nanometers(nm); and a closed nano-fluidic channel formed within said open channelcomprising: a conformal, voidless material film deposited on thesidewalls and the bottom of said open channel; and a material membranecontiguous with said conformal thin film and extending across saidopening, wherein said closed nano-fluidic channel comprises a finalcross-sectional shape that is substantially the same as said initialcross-sectional shape of said open channel.